Electric furnace.



C. F. J. PORSSELL.

ELECTRIG FURNACE.

nrmonxon FILED JULY 20, 1908.

982,420. Patented Jan. 24, 1911. V

2 BHEETS*SHEET 1.

C. F. J. FORSSELL.

ELECTRIC FURNACE.

APPLICATION FILED JULY no, 1908.

Patented Jan. 24, 1911.

2 8HBETSSHEET 2.

welfor? UNITED STATES r grnis'r OFFICE.

l; FREDRIK JA'KOB FORSSELL, OF CLEVELAND, GTE-I10, .'iSSIGNOR TO THE CARBON COMPANY, A CORPORATION OF NEW JERSEY.

NATIONAL ELECTRIC FURNACE.

Specification. of Letters Patent.

Patented J an. 24:, 1911.

Fur/n it concern:

lie it known that .1 CARL FREDRIK JAKou liouszu-zm, a subject of the King of Sweden,

filing ut-Clcrclanvl, in the county of ()uyugzi and State of Ohio, have invented a cernew and useful Improvement in Eleo- Ihurnaces, of which the following is a clear, and exact description.

object of the present invention to m ue'un improvernciu: in electric furnaces are used for heating articles contained. esp ciully furnaces used for such us inalieit do *rublc to have all of r. s heated to the same temperature. pc or he furnace in question is that used nietullizing carbon filaments which is in shape, audit is my purpose to ice improvements in this furnace shall render it possible to produce :i temperature throughout the workon oi the furnace, thereby avoiding ml heat treatment of the articles ed therein.

5 lie above stated object together with 1. re 1 is u plan View of a bank 011": clectuhe furnaces constructed according to invention. is an enlarged. longi .aiual section of a form of my furnace showi the resistor tubes held between the water coo terminals. Fig. 3 is an eleva- 'il u chewing the tube with a packing slot, lhrough which the articles to be treated. are Fig, i l is u crossse'ctiori of the Ti 'ing the packing slot. Fig. 5 is a longitudinal section showing 11 modiin in which :1 carbon plug or rod is cl hetween the end of the resistor l the water cooled terminal.

;.:ic tuhe furnace hi 'herto known, l he e material dirt rcnce in the of the articles treated therein so u uniformity 01 product is not to he u on, This is especially true in the iuetullixing carbon filament:

which demands uniformity .i r of the product more than lOS'i. :e s. I have found that the unuuii orim m in iihe quality of, the filaments packed.

discovered thzit'in the working of in such a tube furnace results in port from the ununi'forinity of the temperature at the difiereut points of the furnace, and inasmuch, therefore, as the nttsiinment of a uniform texnpeiuture throughout that portion of the tube in which filaments are packed would markedly improve the product, it has been my purpose to so construct the furnace that this luck of uniformity in temperature shall not occur. I have obtained this ObjGClT without necessitaiing any clmnge in the conventional construction of the furnace terminals or leads, us will rippeer in the draw resistor tubes have heretofore been open throughout, having eech end chuinfcred so to fit in a carbon bushing with n a water cooled terminal to which a heavy electric current is supplied by means of suitable leads fitted thereto "Water cooling udvsntegg erms for thepreseivation of the lends but it nevertheless increases lhe divergence oi? temperature in the different parts of the :liurnace. That portion of the tuhc nearest the end has its'hent ubs'rectcd by means of the water cooled ter uiinul, while the temperature of the middle zone oi the tube may rise to the full mine which it should hrweconsidering the flow of current and the resistance of the tube.

In my construction, as illustrated, the reference letter A represents thewoll of a hunk of furnaces having therein oppositely positioned water cooled terminals B with a tapered socket at each end and the outer socket ll huving fitted thereto the tapered brass plug ii of the current lead. ln the inner socket B oi? each terminal is filled a carbon luiishiug (I, in which bushings are filled the chzuuiered ends of the supporting ,u'ieans for the inuteriul to he treated, said means being the container or CRIlIlOD resistor tuie l), in that form of construction shown in Fig. 3, or the rods F, in the form shown in liigs, 2 and which rods support the cone tuiner or resistance tube D. These'tube furnaces ere prefer; bl'y, for convenience in churgin them, provided with a slot D out lengthi by means of two longitudinal cuts two transverse cuts at each end thereor' in: with a thii" steel disk-sew. lfhe sti p cl: on thus'cuh'out is subsc- (pseutly used the slot, utter the peel; ing oi the filaments has been, completed.

each end of the tube immediately aidjacent to the working portion, I cut an annula r groove E of a suitable width and depth.

in the case of the ordinary carbon tube liaving, say an effective length of 30 inches with an outside diameter of 2-1/2 inches, a l/l inch wall and consequently with an internal diameter of 2 inches, I should make this groove approximately 1 inch wide with a depth of about 3/32 inches, thus increasl g the resistance of the tube at this point so that the generation 'of heat thereabout will be decidedly greater than at any other part of the tube. By properly proportioning the dimensions of the tube and grooves, the heat generated will be suiticient to raise the tem-- perature at the grooves in spite of the loss of heat to the terminals, to the same polntat- "tained along the middle section of the tube which has a less resistance. The heat generated at the grooves being sufiicient to maintain this-temperature, in spite of the loss of heat on account oi conduction to the terminals, there will he no loss of heat from the middle or working portion of the tube, except to the surrounding medium, and a uniform temperature will be produced along the full length of this working section. The proper dimensions of the groove, of course, will vary with different materials and for different conditions; and these dimensions should be determined by trial with each n aterial and for each condition before a standard is adopted for that material and condition.

In view of the fact that tubes are rarely perfectly cylindricahthe cutting of a groove by turning or grinding is liable to reduce the thickness of the wall irregularly, resulting in a consequent irregular working of the furnace. I have, therefore, devised a modified form of construction illustrated in Fig. 5, in which a. solid carbon rod or plug F, with perhaps a fine hole through the center, to provide for expansion serted between the terminals and the tube. These rods are grooved circumferentially at- F so as to attain at the groove, a temperata e equal to that of the tube after allowing the conduction of the heataway from this point to the terminal. Since the crosssection of the shell of the tube of the dimensions previously stated, is the same as that of a so d rod cut with a diameter of 1-1/2 inches, the groove in this solid rod or plug should, preferably, be of such depth as to give it substantially a diameter of 1-1/4 inches, thus insuring the proper rise in temperature.

' From the foregoing description, it will be plain that the means for supporting the material to be treated. may assume the form such as shown in Fig. 3, in which a one-piece construction is shown, or it may assume the form shown inFigs. 2 and 5, which illustrates a three-piece construction, but in any under heat, is in event, Iintend by the phrase supporting means to include any of the forms shown in Figs. 2, 25 and 5.

lVith the construction described it will be seen that the object of invention and the advantages sought are attained without in any manner interfering with the conventional forms of furnace fittings.

Having thus described my invention, I claim 1. An electric furnace comprising a body adapted to contain the material under treatment, electric terminals, the said body having a conductive wall, conducting means interposed between the terminal and the wall having a resistance sufficient to cause generation of the heat necessary to maintain a temperature in a zone adjacentto said wall as high as that of the wall itself.

2. An electric furnace comprising a tubular body having a wall of resister material, electric terminals, and rods interposed between but in electrical connection with the resister wall and the electric terminals, said rod having at some portion sufiicientresistance to generate the heat necessary to prevent loss, by conduction to the terminals, of the heatgenerated in the resister wall.

3. An electric furnace comprising electric terminals, resister means between the terminals for sustaining the material under treatment and for heating the material, and means interposed between the terminals and the resister means having a resistance sutii-' cient to cause generation of the heat necessary to maintain a temperature adjacent to the resister means as high as that maintained by the resister means itself.

4. An electric furnace comprising electric terminals, resister means between the terminals for sustaining the material under treatment and for heating the material, and means located between theterminals and the heating portion of said resister means having a resistance sutlicient to cause generation of the heat necessary to prevent any loss, by conduction to the terminals, of the heat gen erated in the said resister means.

5. An electric furnace comprising a heating chamber having resister. material in its wall suitable for causing the generation of, heat upon the passage of the electric current, electric terminals, and means for conducting the current from the terminals to said resister material comprising a portion having a reslstance suliicient to cause the generation of the heat necessary to prevent loss, by conduction to the terminals, of the heat generated in the said resister material.

6. An electric furnace comprising'a tubular body having a wall of resister material, electric terminals, conductin means interposed between the resister wafi and each terminal having a resistance suflicient to cause generation of-the heat necessary to p'revent Iossfrom the tubular body by conduction to the terminals.

7 ,An electric furnace com risingelectric terminals, sugporting means or thematerial to be treate having conducting walls and electrically connected with the said terminals, the walls of said supporting-'ineans be ing formed'so as to effect a greater resistance to the passage of an electric current at points near the terminals than the resistance of the other portions of the said walls.

8. An electric furnace comprising electric signature in the presence of two witnesses.

CARL FREDRIK JAKOB FORSSELL.

Witnesses:

J. M. VVOODWARD, Y G. PHILLIPS. 

